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Over 90% of all malignant tumors in the head and neck region are squamous cell carcinomas (HNSCC), ranking within the top 10 of most common cancers worldwide. HNSCC arise in the mucosal linings of the upper aerodigestive tract, and known risk factors are tobacco use, excessive alcohol consumption and infection with high risk types of the human papillomavirus (HPV). Despite the application of intensive treatment protocols, the 5-years survival rate of HNSCC patients has hardly increased last decades and remained at approximately 50%. Therefore, new therapeutic possibilities are urgently awaited. Previously, we identified CHEK1 as a candidate therapeutic target for HNSCC in a whole genome siRNA screen (Martens-de Kemp et al, Clin Cancer Res 2013). Additionally, a functional screen using a microRNA expressing library indicated that knockdown of ATM expression may cause a lethal effect in HNSCC cell lines as well (Lindenbergh-van der Plas et al, Clin Cancer Res 2013). The aim of the present study was to investigate whether interference with the ATM/ATR/CHEK1/CHEK2 DNA damage response pathway is indeed a promising therapeutic approach in HNSCC. RNA interference using siRNAs targeting ATM, ATR, CHEK1 and CHEK2 confirmed that particularly CHEK1 is essential for the survival of a subset of HNSCC cell lines, whereas the cell viability of primary oral keratinocytes and fibroblasts was not compromised. This was confirmed in vitro by treatment with a small molecule inhibitor targeting Chk1, and a therapeutic window between cancer and normal oral mucosal cells was observed. Functional assays indicated an S-phase delay in Chk1 inhibited HNSCC cells, followed by DNA damage. The latter was indicated by elevated phosphorylation of ATM Ser1981 and γH2Ax Ser139, as well as the appearance of chromosomal breaks. The DNA damage response initiated caspase-mediated apoptosis, resulting in programmed cell death. In summary, our data show that HNSCC cells appear to depend strongly on a functional Chk1 protein during DNA replication. Therefore, Chk1 inhibition seems an interesting therapeutic strategy for HNSCC, at least in a subset of tumors. Citation Format: Anne M. van Harten, Marijke Stigter-van Walsum, Marijke Buijze, Boudewijn Jm Braakhuis, Ruud H. Brakenhoff. Chk1 inhibition: a promising targeted treatment for head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4637.

Primary head and neck squamous cell carcinomas (HNSCC) and local relapses develop in preneoplastic fields in the mucosal linings of the upper aerodigestive tract. These fields are characterized by tumor-associated genetic changes, show frequently dysplastic features and are occasionally macroscopically visible as lesions. Currently, there are no adequate treatment options for these fields to prevent tumor development. To develop a targeted therapeutic approach we established four unique preneoplastic cell lines, derived from fields adjacent to HNSCCs. Next, we performed a screen with a selective panel of small interfering RNAs (siRNAs) that are lethal for HNSCC cells, to identify genes essential for survival of preneoplastic cells and not for normal cells. One of these selective essential genes was Polo-like kinase 1 (PLK1). Inhibition of PLK1, both with siRNAs as well as small molecule inhibitors, caused cell death of preneoplastic and HNSCC tumor cells, while primary fibroblasts and keratinocytes were hardly affected. Targeting PLK1 caused a strong G2/M cell cycle arrest in preneoplastic cells accompanied by formation of monopolar spindles during mitosis. Hence, PLK1 is a promising therapeutic target for chemopreventive eradication of preneoplastic fields in patients at high risk of developing HNSCC and local relapses. Citation Format: D Vicky de Boer, Sanne R. Martens-de Kemp, Marijke Buijze, Marijke Stigter-van Walsum, Elisabeth Bloemena, C René Leemans, Boudewijn J.M. Braakhuis, Ruud H. Brakenhoff. Targeted therapy of precancerous fields in the mucosal linings of the head and neck. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4638.

A DNA double-strand break (DSB) is highly cytotoxic; it emerges as the type of DNA damage that most severely affects the genomic integrity of the cell. It is essential that DNA DSBs are recognized and repaired efficiently, in particular, prior to mitosis, to prevent genomic instability and eventually, the development of cancer. To assess the pathways that are induced on DNA DSBs, 14 human lymphoblastoid cell lines were challenged with bleomycin for 30 and 240 minutes to establish the fast and more prolonged response, respectively. The proteomes of 14 lymphoblastoid cell lines were investigated to account for the variation among individuals. The primary DNA DSB response was expected to occur within the nucleus; therefore, the nuclear extracts were considered. Differential analysis was done using two-dimensional difference in gel electrophoresis; paired ANOVA statistics were used to recognize significant changes in time. Many proteins whose nuclear levels changed statistically significantly showed a fast response, i.e., within 30 minutes after bleomycin challenge. A significant number of these proteins could be assigned to known DNA DSB response processes, such as sensing DSBs (Ku70), DNA repair through effectors (high-mobility group protein 1), or cell cycle arrest at the G2-M phase checkpoint (14-3-3 ζ). Interestingly, the nuclear levels of all three proteins in the INHAT complex were reduced after 30 minutes of bleomycin challenge, suggesting that this complex may have a role in changing the chromatin structure, allowing the DNA repair enzymes to gain access to the DNA lesions. (Cancer Res 2006; 66(3): 1473-80)

Patients with Fanconi anemia (FA) are prone to develop malignancies at an early age. Besides hematologic malignancies, squamous cell carcinomas in the anogenital region and head and neck are also frequently found in these patients. The aim of this study was to generate a panel of head and neck squamous cell carcinoma (HNSCC) cell lines and xenografts of FA HNSCC, and to characterize these cell lines in comparison with a panel of seven cell lines from patients with sporadic HNSCC. Analyses have been done on sensitivity to DNA cross-linking agents, loss of heterozygosity profile, TP53 mutations, TP53 polymorphisms and the presence of human papillomavirus. Four FA HNSCC cell lines were established. Sensitivity to DNA cross-linking agents (cisplatin) in the FA HNSCC cell lines was on average 10 times higher as compared with the sporadic HNSCC cell lines. Human papillomavirus was not detected in any of the FA or sporadic cell lines. No differences were found in loss of heterozygosity pattern, TP53 mutation frequency and TP53 polymorphism between FA and sporadic HNSCC cell lines. This is the first report on the generation of squamous cell lines of FA patients. The FA HNSCC cell lines we have generated may be utilized for future studies and might aid in the development of new preventive therapies for FA patients. The genetic characteristics of these cell lines suggest that FA HNSCC are not very different from sporadic HNSCC, except for the sensitivity to cisplatin which is consistent with the known cellular FA phenotype.

The concept of "field cancerization" was first introduced by Slaughter et al. [D. P, Slaughter et al., Cancer (Phila.), 6: 963-968, 1953] in 1953 when studying the presence of histologically abnormal tissue surrounding oral squamous cell carcinoma. It was proposed to explain the development of multiple primary tumors and locally recurrent cancer. Organ systems in which field cancerization has been described since then are: head and neck (oral cavity, oropharynx, and larynx), lung, vulva, esophagus, cervix, breast, skin, colon, and bladder. Recent molecular findings support the carcinogenesis model in which the development of a field with genetically altered cells plays a central role. In the initial phase, a stem cell acquires genetic alterations and forms a "patch," a clonal unit of altered daughter cells. These patches can be recognized on the basis of mutations in TP53, and have been reported for head and neck, lung, skin, and breast cancer. The conversion of a patch into an expanding field is the next logical and critical step in epithelial carcinogenesis. Additional genetic alterations are required for this step, and by virtue of its growth advantage, a proliferating field gradually displaces the normal mucosa. In the mucosa of the head and neck, as well as the esophagus, such fields have been detected with dimensions of7 cm in diameter, whereas they are usually not detected by routine diagnostic techniques. Ultimately, clonal divergence leads to the development of one or more tumors within a contiguous field of preneoplastic cells. An important clinical implication is that fields often remain after surgery of the primary tumor and may lead to new cancers, designated presently by clinicians as "a second primary tumor" or "local recurrence," depending on the exact site and time interval. In conclusion, the development of an expanding preneoplastic field appears to be a critical step in epithelial carcinogenesis with important clinical consequences. Diagnosis and treatment of epithelial cancers should not only be focused on the tumor but also on the field from which it developed.

The five-year survival rate for non-small cell lung cancer (NSCLC) is still less than twenty percent in part due to treatment failure and lack of biomarkers for personalized therapy. Most NSCLC patients are treated by chemotherapy and cisplatin is still the major component of most chemotherapy regimens. However, resistance to cisplatin is a common phenomenon. Aim of this study was to identify protein biomarkers that can be used for cisplatin response prediction. The proteomes and secretomes1 of a series of human NSCLC cell lines with a range of IC50-values for cisplatin (1.5 - 15 μM) were analyzed by label-free proteomics based on GeLC-MS/MS and quantified by spectral counting. Significant differential expression of proteins was determined by the in-house developed beta-binomial statistical test2. Network and gene ontology analysis was performed, with STRING and DAVID respectively, to reveal cellular and molecular functions associated with the differential proteins. In total, 2885 and 2342 proteins were detected in the cell lysates and secretomes, respectively. The proteins with significantly higher expression in the resistant cell lines were associated RNA processing and vesicle transport, while the proteins with higher expression in the sensitive cell lines were known to be involved in RNA splicing, DNA damage repair and extracellular matrix organization. The most promising candidates are being validated in tissues and sputum of patients with known response to cisplatin. 1 Piersma SR et al. J Proteome Res. 2010 Apr 5;9(4):1913-22. 2 Pham TV et al. Bioinformatics. 2010 Feb 1;26(3):363-9. Citation Format: Tieneke B M Schaaij-Visser, Remco Nagel, Inge de Reus, Sander R. Piersma, Thang V. Pham, Egbert F. Smit, Frederik B. Thunnissen, Ruud H. Brakenhoff, Anton Berns, Connie R. Jimenez. Novel candidate protein biomarkers for cisplatin response prediction in non-small cell lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2488. doi:10.1158/1538-7445.AM2013-2488

Introduction: Patients with advanced head and neck squamous cell carcinoma (HNSCC) are treated with cisplatin-containing chemoradiation protocols, but tumor responses can be short-lasting. For these patients surgery combined with postoperative radiotherapy is preferred over chemoradiation. Currently, there are no strong predictors of chemoradiation response that would allow to personalize treatment. We performed a functional genetic siRNA screen to identify genes that can be used to predict upfront which tumors are likely to respond to chemoradiation. Methods: A large panel of HNSCC cell lines was characterized for cisplatin sensitivity. A suitable HNSCC cell line was selected and forward transfected with a genome-wide library of short interfering RNAs (siRNAs), followed by cisplatin (IC20 and IC80) or mock treatment. Genes influencing cellular response to cisplatin were identified by comparing cell viability between the different conditions. The screen was carried out in duplicate and data were analyzed by Z-score calculation using two independent statistical methods. Results: Scrambled siRNAs and siRNAs targeting genes known to influence cell viability or cisplatin sensitivity were included as controls and gave the expected results: less than 10% toxicity and >80% knock-down. Hit lists obtained with both methods of data analysis revealed 86 siRNAs that appeared to influence cisplatin response significantly. Some of these 86 siRNAs target genes that are known to cause sensitivity to cisplatin, thereby confirming the reliability of the approach. We also obtained a list of 80 genes that influenced basic cell viability of HNSCC cells independent of cisplatin. Conclusion: By specifically knocking down all human genes in HNSCC cells, we obtained an unbiased list of at least 86 candidate genes that seem to influence the cellular response to cisplatin. Refined statistical analysis combined with bioinformatics, the exclusion of off-target effects, as well as confirmation of the hits in multiple cell lines is needed to validate these results. Validated hits will be evaluated as predictive markers in clinical samples. This research was supported by the Center for Translational Molecular Medicine (AIRFORCE project). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1750. doi:10.1158/1538-7445.AM2011-1750

Background: TP53 is a key gene in cellular homeostasis and is frequently mutated in head and neck squamous cell carcinoma (HNSCC). There is a variety of TP53 mutations, each with its own biological and clinical implication. Some HNSCC are TP53 wild type, amongst those caused by infection with the human papillomavirus (HPV). Aim of the study was to assess the prognostic significance of TP53 mutations in HNSCC and to identify the most relevant mutation. Methods: TP53 mutation status was assessed by direct sequencing in 141 consecutive HNSCC treated by surgery with radiotherapy when indicated and with a known HPV-status. The type of mutation was correlated with overall survival in a multivariate two-sided Cox regression analysis with wild type as reference. Results: HPV infections was found in 12 out of 141 cases (9%). Although a relation between HPV infection and a favorable prognosis was observed, the association was not significant. A TP53 mutation was found in 88 (62.4%) of the carcinomas and was not associated with survival. Tumors with a mutation resulting in a truncated protein (n=36, 25.5% consisting of nonsense, frame shift and splice site mutations), had a significantly worse overall survival (Hazard ratio: 2.54 with 95% confidence intervals of 1.28 and 5.05, p=0.008). Multivariate analysis showed that a truncating mutation is an independent risk factor, adjusted for HPV status. A missense (i.e. non-truncating) mutation did not influence prognosis. Other ways of mutation classification (disruptive vs. non-disruptive, hotspot vs. non-hotspot and DNA-binding vs. non-DNA-binding) were less discriminative and co-factors, including HPV-status were confounding in these associations. Conclusion: Truncating mutations in the TP53 gene are an important independent predictor for a poor prognosis of HNSCC patients. This patient group is an ideal target population for adjuvant therapy with chemoradiation or viral vector mediated TP53 gene transfer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 338. doi:10.1158/1538-7445.AM2011-338

Lung cancer is currently the number one cause of cancer-related deaths worldwide. Five-year survival rates for both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) are still less than twenty percent due to late stage of presentation, treatment failure and lack of biomarkers for personalized therapy. Aim of this study is to identify protein biomarkers that can be used for treatment response prediction and therapy monitoring. Rather than following a broad strategy by analyzing the proteome of whole cell or tissue lysates, we chose to use a more specific approach based on the assumption that the best tumor markers are shed or secreted by the tumor and can be detected in blood. Secretome (i.e. all proteins shed from or secreted by a cell or tissue) proteomics (Piersma SR et al. J Proteome Res. 2010 Apr 5;9(4):1913-22.) was performed on a set of tumors from conditional mouse models for SCLC and NSCLC (Meuwissen R et al. Oncogene. 2001 Oct 4;20(45):6551-8; Meuwissen R et al. Cancer Cell. 2003 Sep;4(3):181-9.), a set of human and mouse SCLC and NSCLC cell lines and a series of human NSCLC cell lines with a range of IC50-values for cisplatin (1.5 – 15 µM). Secretomes were obtained by collecting serum-free media from the cell lines or collecting PBS in which a tumor tissue piece had been incubated. In the secretome samples, up to 2,000 proteins can be identified with 80% reproducibility by label-free, shotgun nanoLC tandem mass spectrometry and quantified by spectral counting. The beta-binomial test (Pham TV et al. Bioinformatics. 2010 Feb 1;26(3):363-9.) is used to find significant differences in protein expression between the different secretomes and network analysis is performed to provide insight into the underlying cellular mechanisms. The secretomes from the mouse models are used to find proteins specifically secreted by either NSCLC or SCLC, while the comparison between the secretomes of the several human and mouse cell lines allows extrapolation of the results from the mouse models to the human situation. Furthermore, the analysis of the cell lines with various cisplatin IC50-values permits selection of the protein markers that are indicative of sensitivity or resistance. The results of the different proteomics analyses will be presented along with the most promising biomarker candidates and an overview of the functional network analysis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5100. doi:10.1158/1538-7445.AM2011-5100

Background: Genetic heterogeneity is a hallmark of cancer and significant evolution occurs locally and at metastatic sites with disease progression. This heterogeneity might contribute significantly to therapy resistance. Since systematic in depth analyses are lacking in head and neck squamous cell carcinomas (HNSCC), we established and tested a protocol that enables comprehensive single cell analyses of cancer cells from primary tumors and metastasis. Material and Methods: From matched primary tumors and lymph node metastases of two HNSCC patients, single cell suspensions were generated and sedimented on positively charged glass slides at low density. Epithelial tumor cells were identified with double-immunofluorescence staining for CD44v6 and CK5/14. Twelve to 14 double-positive cells were isolated via micromanipulation from each tumor and an adapter-linker PCR was used for whole genome amplification of single cells. Sequencing of TP53 was performed on genomic DNA from primary tumors as well on single cell amplification products. An allele-drop-out experiment was performed to control for artificial allelic loss. Fluorescence-in-situ-hybridization (FISH) was used to determine the copy number of chromosome 17 and TP53-gene loci, respectively. Results: Two different heterozygous TP53 mutations were detected in both cases. On the single cell level, we observed an unexpected variation of wild-types, heterozygous mutations and homozygous mutations on the investigated mutation sites. This mutational distribution was significantly different from the allele-drop-out experiment (drop-out rate: 8%). In one we found an expansion of mutated clones in metastasis, and in the other patient a transmission of the genetic changes between the primary tumor and the lymph node metastasis. Interestingly, our preliminary data indicate a polyclonal origin of the metastasis. Conclusion: Our protocol is feasible to study comprehensively genetic heterogeneity between primary tumors and metastases on a single-cell level. The single cell amplification products tested for TP53 mutations can be used for several other genetic studies, including genome-wide methods such as CGH. Our initial data revealed an unexpected intratumoral genetic heterogeneity in primaries and metastases of HNSCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4823. doi:10.1158/1538-7445.AM2011-4823